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PC Power Supply Voltages

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  • Richard Andrew x64R Offline
    Richard Andrew x64R Offline
    Richard Andrew x64
    wrote on last edited by
    #1

    I have a motherboard monitoring program on my PC. Along with temperatures, it tells the measured voltages coming out of the power supply. Here's the question: For the -12v rail, it's hovering around -7 volts and goes as low as -3. For the -5v rail, it's reading -4 volts. Should I consider replacing the power supply? The machine seems to be running fine otherwise.

    The difficult we do right away... ...the impossible takes slightly longer.

    J D 2 Replies Last reply
    0
    • Richard Andrew x64R Richard Andrew x64

      I have a motherboard monitoring program on my PC. Along with temperatures, it tells the measured voltages coming out of the power supply. Here's the question: For the -12v rail, it's hovering around -7 volts and goes as low as -3. For the -5v rail, it's reading -4 volts. Should I consider replacing the power supply? The machine seems to be running fine otherwise.

      The difficult we do right away... ...the impossible takes slightly longer.

      J Offline
      J Offline
      Jochen Arndt
      wrote on last edited by
      #2

      There are different types of sensor chips used on motherboards. It seems that your monitoring program detects a wrong type because your system is operating without problems. You may try another program or better measure the voltage using a multimeter.

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      • Richard Andrew x64R Richard Andrew x64

        I have a motherboard monitoring program on my PC. Along with temperatures, it tells the measured voltages coming out of the power supply. Here's the question: For the -12v rail, it's hovering around -7 volts and goes as low as -3. For the -5v rail, it's reading -4 volts. Should I consider replacing the power supply? The machine seems to be running fine otherwise.

        The difficult we do right away... ...the impossible takes slightly longer.

        D Offline
        D Offline
        Dave Kreskowiak
        wrote on last edited by
        #3

        Those numbers are not correct. I'd verify the values on the 23-pin connector with a good multimeter before trusting that code. The correct voltages for an ATX 2.2 Power Supply are -5, -12, +3.3, +5 and +12, all with a tolerance of 5%. You can get the pinouts for the connectors just by Googling for "ATX Power Supply 12V pinout". Make sure you match the ATX version on the power supply label with the document you're looking at!

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        Dave Kreskowiak

        Richard Andrew x64R 1 Reply Last reply
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        • D Dave Kreskowiak

          Those numbers are not correct. I'd verify the values on the 23-pin connector with a good multimeter before trusting that code. The correct voltages for an ATX 2.2 Power Supply are -5, -12, +3.3, +5 and +12, all with a tolerance of 5%. You can get the pinouts for the connectors just by Googling for "ATX Power Supply 12V pinout". Make sure you match the ATX version on the power supply label with the document you're looking at!

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          Dave Kreskowiak

          Richard Andrew x64R Offline
          Richard Andrew x64R Offline
          Richard Andrew x64
          wrote on last edited by
          #4

          Thanks Dave, I think that's what I will do. I just have to find the motivation to get in there and unplug the motherboard connector.

          The difficult we do right away... ...the impossible takes slightly longer.

          D A 2 Replies Last reply
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          • Richard Andrew x64R Richard Andrew x64

            Thanks Dave, I think that's what I will do. I just have to find the motivation to get in there and unplug the motherboard connector.

            The difficult we do right away... ...the impossible takes slightly longer.

            D Offline
            D Offline
            Dave Kreskowiak
            wrote on last edited by
            #5

            No no no. Do it while it's running. That makes the measurement at the time there is load on the power supply when the voltages will fluctuate the most. Also, if you pop the connector off the motherboard you have to short the PowerGood line to ground to get the power supply to start.

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            Richard Andrew x64R 1 Reply Last reply
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            • D Dave Kreskowiak

              No no no. Do it while it's running. That makes the measurement at the time there is load on the power supply when the voltages will fluctuate the most. Also, if you pop the connector off the motherboard you have to short the PowerGood line to ground to get the power supply to start.

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              Dave Kreskowiak

              Richard Andrew x64R Offline
              Richard Andrew x64R Offline
              Richard Andrew x64
              wrote on last edited by
              #6

              Oh! I was wondering about that. But how can I touch the contacts if the plug is plugged?

              The difficult we do right away... ...the impossible takes slightly longer.

              D 1 Reply Last reply
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              • Richard Andrew x64R Richard Andrew x64

                Oh! I was wondering about that. But how can I touch the contacts if the plug is plugged?

                The difficult we do right away... ...the impossible takes slightly longer.

                D Offline
                D Offline
                Dave Kreskowiak
                wrote on last edited by
                #7

                Through the back of the connector where the wires go in. Just be careful not to miss the connector entirely and touch the probes to the motherboard! :)

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                Richard Andrew x64R 1 Reply Last reply
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                • D Dave Kreskowiak

                  Through the back of the connector where the wires go in. Just be careful not to miss the connector entirely and touch the probes to the motherboard! :)

                  A guide to posting questions on CodeProject

                  Click this: Asking questions is a skill. Seriously, do it.
                  Dave Kreskowiak

                  Richard Andrew x64R Offline
                  Richard Andrew x64R Offline
                  Richard Andrew x64
                  wrote on last edited by
                  #8

                  OK I'll give it a try. Thanks. :)

                  The difficult we do right away... ...the impossible takes slightly longer.

                  D 1 Reply Last reply
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                  • Richard Andrew x64R Richard Andrew x64

                    OK I'll give it a try. Thanks. :)

                    The difficult we do right away... ...the impossible takes slightly longer.

                    D Offline
                    D Offline
                    Dave Kreskowiak
                    wrote on last edited by
                    #9

                    no problem

                    A guide to posting questions on CodeProject

                    Click this: Asking questions is a skill. Seriously, do it.
                    Dave Kreskowiak

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                    • Richard Andrew x64R Richard Andrew x64

                      Thanks Dave, I think that's what I will do. I just have to find the motivation to get in there and unplug the motherboard connector.

                      The difficult we do right away... ...the impossible takes slightly longer.

                      A Offline
                      A Offline
                      Albert Holguin
                      wrote on last edited by
                      #10

                      FYI... if your power was that far off, you'd probably have major problems. Things would flicker on/off or alternatively smoke would start coming out of the power supply or associated regulators (if it was a short causing fluctuations).

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